Communication device with synchronized zero-crossing demodulator and method

A communication device for receiving an information signal, comprising:

• a first mixer for producing a first, in-phase component;
• a second mixer for producing an out-of-phase component;
• a multi-level detector for detecting the contents of the information using the in-phase and out-of-phase components, the detector comprising:
• means for detecting the direction of instantaneous phase rotation at zero-crossings;
• means for accumulating all of the zero-crossings, based upon a symbol transition time, for generating an edge clock signal representative of the symbol transition time, only when at least two, non-zero consecutive zero-crossing samples are detected in which the first sample is of one phase and the second sample is of the other phase, and for estimating phase angle rotation of the information signal based upon all of the accumulated zero-crossings since a previously generated edge clock signal;
• and
• means for decoding the estimated phase angle rotation of the information signal for determining the contents thereof.

A method for detecting the contents of an information signal, comprising the steps of:

• generating an IF signal having in-phase and out-of-phase components;
• monitoring the in-phase and out-of-phase components to determine instantaneous phase rotation direction at zero-crossings;
• accumulating all of the zero-crossings of the information signal, generating an edge clock signal only when at least two, non-zero consecutive zero-crossing samples are detected in which the first sample is of one phase and the second sample is of the other phase, and estimating phase angle rotation of the information signal based upon a generated edge clock signal, and from all of the zero-crossings since a previously generated edge clock signal;
• and
• decoding the contents of the information signal from the estimated phase angle rotation.